Changguo Chen

Mesoporous vanadium pentoxide nanofibers with significantly enhanced Li-ion storage properties by electrospinning†

Mesoporous V2O5 nanofibers were fabricated by a method combining sol–gel processing with electrospinning followed by annealing in air. The resultant nanofibers were 350 nm in diameter and consisted of porous polycrystalline vanadium oxide with a specific surface area of ∼97 m2 g−1. The mesoporous V2O5 nanofibers demonstrated a significantly enhanced Li ion storage capacity of above 370 mA h g−1 and a high charge/discharge rate of up to 800 mA g−1 with little cyclic degradation.

The Oxygen Reduction Electrocatalytic Activity of Cobalt and Nitrogen Co-doped Carbon Nanocatalyst Synthesized by a Flat Template

The design of noble-metal-free catalysts for oxygen reduction reaction (ORR) is very important to the commercialization of fuel cells. Here, we use a Co-modified montmorillonite (Co-MMT) as a flat template to prepare Co- and N-doped nanocarbon ORR catalysts derived from carbonization of polyaniline at controlled temperatures. The use of flat template can hinder the agglomeration of polyaniline during pyrolysis process and optimize the N-rich active site density on the surface. The addition of transition metal Co in the flat MMT template can largely promote the formation of Co–N sites in prepared catalyst, facilitating the effective improvement of catalytic activity towards the ORR with a direct four-electron transfer pathway. The excellent ORR activity may be mainly attributed to high contents of graphitic N, pyridinic-N, and Co-N configurations. This study opens a new way to rationally design cheap and active ORR catalysts by using simple flat compound as a direct template.

Diatomite-Templated Synthesis of Freestanding 3D Graphdiyne for Energy Storage and Catalysis Application

Graphdiyne (GDY), a new kind of two-dimensional (2D) carbon allotropes, has extraordinary electrical, mechanical, and optical properties, leading to advanced applications in the fields of energy storage, photocatalysis, electrochemical catalysis, and sensors. However, almost all reported methods require metallic copper as a substrate, which severely limits their large-scale application because of the high cost and low specific surface area (SSA) of copper substrate. Here, freestanding three-dimensional GDY (3DGDY) is successfully prepared using naturally abundant and inexpensive diatomite as template. In addition to the intrinsic properties of GDY, the fabricated 3DGDY exhibits a porous structure and high SSA that enable it to be directly used as a lithium-ion battery anode material and a 3D scaffold to create Rh@3DGDY composites, which would hold great potential applications in energy storage and catalysts, respectively.

Template Synthesis of an Ultrathin β-Graphdiyne-Like Film Using the Eglinton Coupling Reaction

β-Graphdiyne (β-GDY) is a two-dimensional carbon material with zero band gap and highly intrinsic carrier mobility and a promising material with potential applications in electronic devices. However, the synthesis of continuous single or ultrathin β-GDY has not been realized yet. Here, we proposed an approach for ultrathin β-GDY-like film synthesis using graphene as a template because of the strong π-π interaction between β-GDY and graphene. The as-synthesized film presents smooth and continuous morphology and has good crystallinity. Electrical measurement reveals that the film presented a conductivity of 1.30 × 10-2 S·m-1 by fabricating electronic devices on β-GDY grown on a dielectric hexagonal boron nitride template.

Inexpensive Ipomoea aquatica Biomass-Modified Carbon Black as an Active Pt-Free Electrocatalyst for Oxygen Reduction Reaction in an Alkaline Medium

The development of inexpensive and active Pt-free catalysts as an alternative to Pt-based catalysts for oxygen reduction reaction (ORR) is an essential prerequisite for fuel cell commercialization. In this paper, we report a strategy for the design of a new Fe–N/C electrocatalyst derived from the co-pyrolysis of Ipomoea aquatica biomass, carbon black (Vulcan XC-72R) and FeCl3·6H2O at 900 °C under nitrogen atmosphere. Electrochemical results show that the Fe–N/C catalyst exhibits higher electrocatalytic activity for ORR, longer durability and higher tolerance to methanol compared to a commercial Pt/C catalyst (40 wt %) in an alkaline medium. In particular, Fe–N/C presents an onset potential of 0.05 V (vs. Hg/HgO) for ORR in an alkaline medium, with an electron transfer number (n) of ~3.90, which is close to that of Pt/C. Our results confirm that the catalyst derived from I. aquatica and carbon black is a promising non-noble metal catalyst as an alternative to commercial Pt/C catalysts.

Boosting the oxygen reduction activity of a three-dimensional network Co–N–C electrocatalyst via space-confined control of nitrogen-doping efficiency and the molecular-level coordination effect

The improvement of total nitrogen content and nitrogen-doping efficiency in carbon-based electrocatalysts is greatly significant to boost the electrocatalytic activity for the oxygen reduction reaction (ORR). Here, we report a new strategy for the synthesis of a highly mesoporous cobalt and nitrogen co-doped carbon electrocatalyst (3D-Co–N–C) with a three-dimensional network structure and a high BET surface area (∼638 m2 g−1) via using a novel cobalt-2,4,6-tri(2-pyridyl)-1,3,5-triazine complex with a strong molecular-level coordination effect as a single-source precursor and self-assembled sodium chloride aggregates as a space-confined nanoreactor for effective control of a high-temperature calcination process to reduce the thermal loss of nitrogen atoms and promote the nitrogen-doping efficiency, facilitating boosting of the ORR electrocatalytic activity in alkaline medium. The prepared 3D-Co–N–C catalyst exhibits unexpectedly excellent ORR activity with an onset potential of ∼1.0 V and a half-wave potential of ∼0.83 V, which is comparable to that of the commercial 20 wt% Pt/C catalyst. Additionally, the H2O2 yield (<17.0%) and the average electron transfer number of ∼3.8 for 3D-Co–N–C indicate a quasi four-electron pathway for ORR catalysis, suggesting that 3D-Co–N–C is a promising carbon-based electrocatalyst. It is proposed that the formation of the Co–Nx active structure can effectively enhance the electrocatalytic activity, but high contents of pyridinic- and graphitic-N can be mainly responsible for the ORR activity, which may be the electrocatalytically active site centers for the ORR. Besides, high BET surface area, highly mesoporous characteristics and outstanding electronic conductivity are also significant for the improvement of ORR activity. This study can provide a new, facile and green method for building high-performance carbon-based ORR electrocatalysts derived from easily available and innoxious transition metal–organic complexes, which can also help us to better understand the origin of the activity, active sites and their catalysis mechanism.